Primary paraganglioma of thyroid gland: a clinicopathologic and immunohistochemical study with review of the literature.

Primary paraganglioma of the thyroid is a very rare neuroendocrine tumour. Only 24 cases have been reported in the Literature. A case of a primary paraganglioma of the thyroid is presented in order to provide a review of the Literature, an update on current knowledge and to emphasize the key diagnostic role of immunohistochemistry. A 63-year-old female presented with a 6-month history of right-sided solitary thyroid nodule. Ultrasonography and fine needle aspiration biopsy were not diagnostic. The patient underwent right hemithyroidectomy. The tumour cells showed a strongly positive staining for chromogranin A, synaptophysin and neuron specific enolase, whereas S-100 protein was positive in sustentacular cells. A diagnosis of primary paraganglioma of the thyroid was made. Radiotherapy for suspected local tumour persistence was planned. At 18-months follow-up, the patient is alive without evidence of recurrence. This case highlights the need to include primary paraganglioma of the thyroid in the differential diagnosis of neuroendocrine intra-thyroidal tumours. Immunohistochemistry is essential for diagnosis. Surgery is the treatment of choice.